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Why Am I So Tired After I Work Out?

by JR Landry

About JR Landry

JR Landry began writing professionally in 2010 for various websites. He has extensive experience in sports writing, most notably on football and strength training. Landry began a teaching career after earning his Bachelor of Arts in English from Austin College.

The concept of "no pain, no gain" has long been used by coaches and trainers to push tired athletes to exercise. These coaches and trainers would have you believe that your body is not tired, but your mind is telling you that your body is tired because you are not accustomed to hard physical training. But your body grows tired for a reason. Physical exhaustion is a warning sign to stop what you are doing, and there are several ways in which your body sends the message.

Poor Cardiovascular Fitness

The most likely reason you feel tired after working out is poor cardiovascular fitness. Even lifting weights can stress the cardiovascular system if done with little rest between sets. If you increase the intensity of your workout too quickly, it is not uncommon at all for you to become exhausted. The best way to monitor this is to measure your heart rate periodically throughout the workout. If your heart is beating too rapidly, typically exceeding 180 beats per minute, take a few minutes to rest and drink water to hydrate your body. The rest will allow your heart rate to drop, and the water will rehydrate your body, allowing more blood to pump through your heart.

Lack of Muscular Endurance

When you begin a weightlifting routine, your muscles will likely not be accustomed to repeated loads being placed on them. Muscle strength develops more quickly than muscular endurance. Because of this, your muscles will often fatigue much faster when performing several repeated lifts instead of a few intense exercises. Lactic acid builds up quickly in muscles that are stressed constantly, and this lactic acid causes the severe soreness that is associated with exhaustion during exercise.

Medical Issues

If you have recently recovered from an illness, you probably feel fine during normal activities, but during exercise your body may be too weary to maintain a high level of activity. If you have not been ill recently, consult a physician to determine if the cause of your fatigue could be something more serious, such as cardiomegaly. Typically referred to as an enlarged heart, this disease is common among athletes. Fatigue is a symptom. Undiagnosed, cardiomegaly can pose severe health risks.

Poor Technique

Poor technique is the cause of several issues for which other factors take the blame. Something as simple as your breathing during a workout can increase your level of fatigue significantly. Whether performing cardio or strength training exercises, holding your breath or breathing irregularly can cause your muscles to function less efficiently, requiring more energy. Performing the movements incorrectly can also lead to energy depletion. For instance, running with poor technique, such as with your arms swaying wildly or not moving in a straight line, can make less intense workouts feel more tiring.